jn2nOh and the superstition with salt seems to go back partly to Christian beliefs and partly to how valuable salt used to be as a commodity.

jn2nI'd say a tradition is a ritual that we continue because it has been passed down the generations. It can be superstitious but needn't be. A superstition is something we believe or do irrationally, to achieve or avoid a certain outcome, or something we attach significance to without evidence.